The Hot Metal Desulfurization

Sulphur is mainly present in the iron ore and in the coal. Reducing the sulphur content to less than 0.020% in the blast furnace is difficult from an economical standpoint. As the steel quality often requires a sulphur content of 0.010%, the hot metal must be desulphurized in another way.

Lime is used in various desulphurization methods alone or with a lime/magnesium mix. Using "fluidized" lime and magnesium reduces the cost of the treatment compared to the process using calcium carbide (also decreases explosion risks due to the use of calcium carbide) .  This technique also has less environmental impact. 

They are injected into the metal with lances under a gaseous stream. In this way, the sulphur content can be reduced to levels below 0.005 %. In order to reduce the loss of hot metal when removing the impurities floating at the surface, some fluxing agents are added to the injected mix.  This process reduces the cost of desulphurization.